ImageViewer

import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.swing.*;
import java.io.File;

/**
 * ImageViewer is the main class of the Image Viewer application. It builds and
 * displays the application GUI and initialises all other components.
 *
 * @author Ahmad Lamaul Farid
 * @version 9 Desember 2020
 */

public class ImageViewer
{
    private static final String VERSION = "Version 1.0";
    private static JFileChooser fileChooser = new JFileChooser(System.getProperty("user.dir"));

    private JFrame frame;
    private ImagePanel imagePanel;
    private JLabel filenameLabel;
    private JLabel statusLabel;
    private OFImage currentImage;

    /**
     * Create an ImageViewer show it on screen.
     */

    public ImageViewer()
    {
        currentImage = null;
        makeFrame();
    }

    private void openFile()
    {
        int returnVal = fileChooser.showOpenDialog(frame);

        if (returnVal != JFileChooser.APPROVE_OPTION) return;

        File selectedFile = fileChooser.getSelectedFile();
        currentImage = ImageFileManager.loadImage(selectedFile);

        if (currentImage == null)
        {
            JOptionPane.showMessageDialog(frame, "The file was not in a recognized image file format.", "Image Load Error", JOptionPane.ERROR_MESSAGE);
            return;
        }

        imagePanel.setImage(currentImage);
        showFilename(selectedFile.getPath());
        showStatus("File loaded.");
        frame.pack();
    }

    private void close()
    {
        currentImage = null;
        imagePanel.clearImage();
        showFilename(null);
    }

    private void quit()
    {
        System.exit(0);
    }

    private void makeDarker()
    {
        if (currentImage != null)
        {
            currentImage.darker();
            frame.repaint();
            showStatus("Applied: Darker");
        }

        else
        {
            showStatus("No image loaded.");
        }
    }

    private void makeLighter()
    {
        if (currentImage != null)
        {
            currentImage.lighter();
            frame.repaint();
            showStatus("Applied: Lighter");
        }

        else
        {
            showStatus("No image loaded.");
        }
    }

    private void threshold()
    {
        if (currentImage != null)
        {
            currentImage.threshold();
            frame.repaint();
            showStatus("Applied: Threshold");
        }

        else
        {
            showStatus("No image loaded.");
        }
    }

    private void showAbout()
    {
        JOptionPane.showMessageDialog(frame, "ImageViewer\n" + VERSION, "About ImageViewer", JOptionPane.INFORMATION_MESSAGE);
    }

    private void showFilename(String filename)
    {
        if (filename == null)
        {
            filenameLabel.setText("No file displayed.");
        }

        else
        {
            filenameLabel.setText("File: " + filename);
        }
    }

    private void showStatus(String text)
    {
        statusLabel.setText(text);
    }

    private void makeFrame()
    {
        frame = new JFrame("ImageViewer");
        makeMenuBar(frame);

        Container contentPane = frame.getContentPane();

        contentPane.setLayout(new BorderLayout(6 ,6));

        filenameLabel = new JLabel();
        contentPane.add(filenameLabel, BorderLayout.NORTH);

        imagePanel = new ImagePanel();
        contentPane.add(imagePanel, BorderLayout.CENTER);

        statusLabel = new JLabel(VERSION);
        contentPane.add(statusLabel, BorderLayout.SOUTH);

        showFilename(null);
        frame.pack();

        Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
        frame.setLocation(d.width / 2 - frame.getWidth() / 2, d.height / 2 - frame.getHeight() / 2);
        frame.setVisible(true);
    }

    private void makeMenuBar(JFrame frame)
    {
        final int SHORTCUT_MASK = Toolkit.getDefaultToolkit().getMenuShortcutKeyMask();

        JMenuBar menubar = new JMenuBar();
        frame.setJMenuBar(menubar);

        JMenu menu;
        JMenuItem item;

        menu = new JMenu("File");
        menubar.add(menu);

        item = new JMenuItem("Open");

        item.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_W, SHORTCUT_MASK));
        item.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                openFile();
            }
        });

        menu.add(item);

        item = new JMenuItem("Close");

        item.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_Q, SHORTCUT_MASK));
        item.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                quit();
            }
        });

        menu.add(item);

        // Filter menu

        menu = new JMenu("Filter");
        menubar.add(menu);

        item = new JMenuItem("Darker");
        item.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                makeDarker();
            }
        });

        menu.add(item);

        item = new JMenuItem("Lighter");
        item.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                makeLighter();
            }
        });

        menu.add(item);

        item = new JMenuItem("Threshold");
        item.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                threshold();
            }
        });

        menu.add(item);

        // Help menu

        menu = new JMenu("Help");
        menubar.add(menu);

        item = new JMenuItem("About ImageViewer...");
        item.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                showAbout();
            }
        });

        menu.add(item);
    }
}